Hello Pieter-Tjerk, LF,
Another point comes to my mind:
When thinking about the sketch you recently attached (here attached
again), would you agree that here the shape of the probe is not
irrelevant? I mean, a round plate which is in a horizontal position to
ground should cause less potential difference (signal level) then a
vertical thin wire with the same capacity.
BTW, capacity against what is the question. It's not the capacity
against ground but to the far field i think. Here it becomes complex to
me :-)
I try to compare it to a TX antenna. I see the TX antenna as a
capacitor against ground. But the imaginary E field lines that go
directly to ground are "useless", except for reduction of the needed L
for resonance. This can be described as a fixed capacitor parallel to
the loading coil. Ony the field lines that make a faaaaaaaar way will
cause something that is described by a radiation resistance.
So back to the mini whip, the often stated 4 pF must be against
"something useful", which is not the grounded pole. It must catch some
of the field lines of the distant transmitter. And if the E fields of
your sketch are from this transmitter it must be useful to cross as
many as possible of the äquipotential lines, i.e. a long thin vertical
wire should result in more signal voltage as a plate near the pole.
Or not?
73, Stefan/DK7FC
-------- Original-Nachricht --------
[...]
See the attached sketch: the equi-potential lines in the area near the
probe are much closer together because the pole is at ground potential.
[...]
73, Pieter-Tjerk, PA3FWM
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